The Ulam
Spiral is a pattern of prime numbers discovered by a mathematician
while doodling.

In 1963, mathematician Stanislaw
Ulam was doodling on a scrap paper during a "long and very boring
paper" at a science meeting when he realized that he had created
a method to graph prime numbers that revealed a pattern.

(Left) Ulam started by writing a grid of numbers, starting with 1 at
the center and spiraling out
(Center) He selected only the prime numbers and noticed that many of them
form diagonal lines (Right) An Ulam spiral of size 200 x 200, with black
dots representing the prime numbers. Did you notice the high number of
diagonal lines?